The invention relates to the technical field of welding, and discloses a reinforcing mesh welding device for a reinforced concrete building structure. The reinforcing mesh welding device comprises a shell I, a turntable I is movably connected into the shell I, a connecting plate is movably connected to the exterior of the turntable I, and a clamping rod is movably connected to the exterior of the connecting plate; and under the interaction of the shell I, the turntable I, the connecting plate, the clamping rod, a magnet assembly, a ratchet wheel, a clockwork spring, a threaded rod, a sliding block, an electric lifting rod, a welding head, a photosensitive assembly and a lamp bead, the device can automatically perform equidistant welding on a reinforcing mesh according to the requirements of people, so that the reinforcing mesh can be prevented from being manually moved for welding, time and labor are saved, the welding precision is high, the quality of the welded reinforcing mesh can meet the due requirements, meanwhile, waste of reinforcing mesh materials can be avoided, and the manufacturing cost of an enterprise can be reduced.